With the advent of printers and digital copiers which produce sets or jobs at a high page per minute rate of production of printed sheets, there has become an increasing need for post processing machines which interface with the printer or copier and which function to collect the sheets into sets or jobs and finish the sets or jobs by stapling at either of the corners or, if desired, along the edge of a set or job.
On certain machines known in the prior art, the post processing machine also performs hole punching operations to enable the set of sheets or job to be bound into loose leaf binders, after having been stapled or not.
The need for assembling sheets in an assembly station prior to post processing is recognized in Lawrence U.S. Pat. No. 5,649,695, granted Jul. 22, 1997, wherein the machine is capable of continuously assembling sheets in an assembly station, and retracting a support from the trailing end of the sheets while gripping the sets and moving them into a finishing station before releasing the grip on the set and depositing the finished set on a tray.
In Canon U.S. Pat. No. 5,385,340, granted Jan. 31, 1995, for example, it is recognized that sheets may be assembled partially on a stacker tray and partially on a fixed shelf in a position for post processing, and then the processed sets may be pushed or displaced from the fixed shelf to the stacker tray.
In Coombs application, Ser. No. 280,599, filed Mar. 29, 1999 and co-owned herewith, it is recognized that sheets may be assembled on a stacker tray and on a shelf on which the sets of sheets are finished, as by stapling at their trailing end, and the stapled set is then dropped or dumped for dropping the set from the shelf completely onto a stacker tray.
In Coombs application, Ser. No. 078,202, filed May 14, 1998 and co-owned herewith, there is shown a sequentially operated apparatus in which sets of sheets or a job are assembled on a first tray which is then opened to drop sheets to a second tray for finishing. The second tray opens to drop the finished set onto a stacker tray.
The present invention relates to utilization of two stations, each having a shelf which is capable of being dumped. On the top shelf sheets are assembled in a number which may be less than an entire set so that as subsequent sheets making up a complete set are fed to the top shelf and dumped to the lower second shelf on which the completed set may be finished, so as to ultimately create a completed set, while additional sheets used in the composition of the next set are being fed onto the top shelf.
While the first referred to set is on the second shelf, the sheets can be progressively jogged into edge alignment, stapled, offset, if desired, and then dumped onto a stacker tray.
In such an apparatus, using a punch mechanism as the sheets are being fed to the top shelf, the sheets can also be punched on the fly so as to not inhibit the speed of input of the sheets from the printer or copier to the top shelf.
In the case that the sheets require inversion, which is a function of whether the sheet is exiting the printer or copier face up or face down, the post processing machine of the invention can include a simple inverter structure located so as to invert the sheets as they exit the printer or copier without inhibiting the speed of the printer or copier itself.